"Four months ago Joey persuaded her it was time to take off some of her hair; he said it was just getting too long," said the source.

"While Joey was snipping away the idea came to her of doing some good with it rather than throwing it away.

Getty - Pool

The Duchess of Cambridge arrives at the Mother and Baby unit at the Bethlehem Royal Hospital last week

"She mentioned it to Joey, who thought it was a brilliant idea."

The source added that the donation was made anonymously by Kate.

The mum-to-be has made a number of public engagements alone and with her husband Prince William, 35, over the past few months - including to schools and to the mother and baby unit at Bethlem Royal Hospital last week.

The source said: "It was sent using someone else's name, so that the trust didn't know it was from a royal source – they just thought it was from a female donor in the Kensington area."

Getty - Contributor

Pop star Harry Styles wowed his fans when he shared a picture of his ponytail, that he donated to the Little Princess Trust

"It's lovely to think somewhere a little girl is happily wearing a wig made from a real princess's hair.

"It's a very heartwarming thing for Kate to have done, and very thoughtful to use hair that would have otherwise just been thrown away."

The charity was set up 12 years ago by the parents of Hannah Tarplee, who died at the age of 5 from a cancerous tumour.

They have since donated 5,500 real hair wigs to sick children and towards finding causes and cures for paediatric cancer.

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The charity has said it is not aware of a donation from the Duchess of Cambridge.

A spokesperson for the charity said: "We are not aware of having any donation made by the Duchess of Cambridge, but if she had sent us some hair, she may have decided to make it anonymously, understandably after the attention given to the donation made by Harry Styles."

A spokesman for Kensington Palace told Sun Online they were unable to comment.

Moment students line up for handshakes and hugs with Kate during school visit to Bond Primary School in Mitcham

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